Is this undefined?

I think what I am doing is legal, but I am not 100% sure. I have function "A" that sets a pointer from a returned pointer location from function "B".

Code:

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void A(void)
{
    char *myvar;
        myvar = B();
}

char *B(void)
{
    char *myvar2;
        myvar2 = malloc(100);
    return myvar2;
}

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Also, I thought that a neater method would be if B returned nothing but modified A's pointer's address. Could B malloc some space at a pointer passed to it?

If I am unclear, let me know.

What makes you think that it might result in undefined behaviour? At a glance, it looks perfectly fine, except that B() is really only casting the pointer returned by malloc() to char*, and pretty much does nothing else.

Quote:

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Originally Posted by carrotcake1029

Could B malloc some space at a pointer passed to it?

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Yes, but you would need to pass a pointer to a pointer so that the pointer in A()'s scope can point to the object returned by the malloc() call in B().

That was just an example, obviously I will do more.

So would something like this be what you are talking about for the function to be able to allocate space. I may just avoid this, I think it could get ugly in some cases.

Code:

---

void A(void)
{
    char *myvar;
        B(&myvar);
        //Is this a pointer to a pointer, or would i need to do char **myvar?
}

void B(char **myvar2)
{
    *myvar2 = malloc(100);
}

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Quote:

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Originally Posted by carrotcake1029

So would something like this be what you are talking about for the function to be able to allocate space.

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Yes.

Quote:

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Originally Posted by carrotcake1029

I may just avoid this, I think it could get ugly in some cases.

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It depends. You also should provide a size argument (a pointer too) so that B() can set it, otherwise A() would have no idea how many elements were allocated.